“What is the effect of molecule size on a molecule’s ability to diffuse across a semipermeable membrane?” If molecules are small enough, then

They get pregnant at younger ages

The answer to this will be from your lab notes/procedure. it would be best to ask another student who participated in the lab as we do not know what was done, what enzyme or if the temperature is celsius or fahrenheit. if i were to guess though i'd say the rate stopped due to enzyme denturing at high temperature